This article first appeared in the Winter, 2009–2010 issue of Generations, ASA’s quarterly journal; the entire issue was devoted to the topic, “Gray and Green: The Intersection of Aging and the Environment.” ASA members receive Generations as a membership benefit; non-members may purchase subscriptions or single copies of issues at our online store.

Climate change has the potential to affect the environment in a number of ways that place increased stress on everyone, but disproportionately on the most vulnerable populations, including the young, the old, those with chronic illness, and the poor. Older people are among the most at risk because of decreased mobility resulting from age, changes in physiology, and more restricted access to resources, all of which may limit adaptive capacity. The challenges older people will face adapting to climate change have potentially far-reaching implications for the health of individuals and the population as a whole. A number of societal strategies to cope will be required. Habitability, health, and environmental justice will be challenged as the adverse effects of climate change interact with factors that are characteristic of older people.

Overview of Climate Change

The Intergovernmental Panel on Climate Change (IPCC) (2007a), a scientific body formed to evaluate the risks of climate change, has prepared their fourth assessment on the scientific, technical, and socioeconomic information relevant for the understanding of the risk of human-induced climate change. Their findings indicate that use of fossil fuel, agricultural practices, and changes in land use have been the dominant cause of the increase in greenhouse gases emitted to the atmosphere over the past 250 years. Global mean surface temperatures have continued to rise as these associated emissions have increased. Eleven of the last twelve years rank among the twelve warmest years on record since 1850. Since the 1970s, droughts have become more common, especially in the tropics and subtropics. Furthermore, since 1961, global average sea level has risen at a mean rate of 1.8 millimeters per year and even higher since 1993, at 3.1 millimeters per year, with contributions from thermal expansion, melting glaciers and ice caps, and the degeneration of the polar ice sheets. These findings indicate that unabated climate change will have serious impacts on the environment and on food production, political stability, and human health.

Heightened Vulnerability

For older adults, the changing climate brings heightened vulnerability to environmental risks, which include extreme weather events, exacerbated vector-borne diseases, compromised agriculture, reduced availability of fresh water, and decreased habitability of human population centers. Older people are more vulnerable to the effects of temperature extremes and have a significantly higher mortality risk in extreme weather events. The older population is also at greater risk because of increased susceptibility to disease and to the effects of stresses on the food and water supply, and reduced ability to mobilize quickly. The health effects of climate change on older people can be classified into two categories: (1) those due to the greater exposure of older people to the threat (“the dose” in public health terminology) and (2) those that are a combination of exposure plus greater reactivity as a characteristic of aging (increased physiological susceptibility) or social factors that vary across individuals (social vulnerability).

Overall, the research literature suggests that greater physiological susceptibility and social vulnerability may best account for many of the negative health effects of climate change on older people. The effects of climate change are variable, depending on pre-exposure health status, psychological well-being, and social characteristics (Geller and Zenick, 2005). Indeed, turning age 65 does not in itself make a person more vulnerable to the negative effects of climate change. Rather, it is the individual physiological and social factors associated with aging that may bring greater negative impact.

For example, the oldest old (age 85 and over) are more likely to suffer negative health effects from climate change (Haq, Whitelegg, and Kohler, 2008) because of physical decline or frailty (McGeehin and Mirabelli, 2001). Those individuals who suffer from multiple pre-existing chronic conditions that limit mobility and those who take medications that increase susceptibility to heat, pollutants, and vectorborne diseases are more at risk because of those factors (Geller and Zenick, 2005; Haq, Whitelegg, and Kohler, 2008).

Social and economic factors increase the vulnerability of some older people because socioeconomic disadvantages restrict the capacity of individuals to avoid the negative health impacts of climate change, mitigate those impacts, or cope with them if they cannot be mitigated or avoided. People who are poorer, less educated, less connected to transportation, and who have smaller social networks will be at greater risk for negative outcomes in natural disasters (Haq, Whitelegg, and Kohler, 2008). The combination of chronic health problems and social isolation may be particularly problematic (Haq, Whitelegg, and Kohler, 2008). To the extent that such factors are disproportionately concentrated among older people, they may be at greater risk.

Other pathways creating vulnerability to climate change threats are likely due not only to the aging process, but also to accumulated exposures over the life course. There is suggestive evidence that physiological susceptibility to the negative health effects of climate change can be programmed in the body by early exposures to neurotoxins and air pollution (Cohn and MacPhail, 1996; Stein et al., 2008). Early exposure to pesticides and other neurotoxins may be associated with a greater probability of neurodegeneration later in life (Stein et al., 2008). This degeneration occurs as environmental toxins and air pollutants produce a heightened inflammatory response; in turn, excess inflammation is associated with cardiovascular disease, diabetes, and conditions such as Alzheimer’s disease. Exposure to neurotoxins and pollution is greater among those of lower socioeconomic status (e.g., Filleul et al., 2004). Built up over decades, the accumulated exposure thus can produce greater susceptibility to health threats in later life (Stein et al., 2008).

Examples of Specific Effects

Studies of the health impacts of extreme heat waves, hurricanes, and air pollution on older people illuminate the role of both physiological and social factors as well as mitigation strategies for individuals and communities. The evidence suggests that understanding the specific ways that climate change affects older people would lead to more effective interventions.

Heat waves

There is evidence that the impacts of exposure to heat are variable in the United States, depending on how well housing structures and communities have accommodated to hot climate conditions over time. For example, McGeehin and Mirabelli (2001), analyzing epidemiological data on heat-related morbidity and mortality, observed that heat-related health events are more likely to occur in the U.S., where extreme heat is unusual and unexpected (for a similar observation in Europe, see Diaz et al., 2002a). An analysis of the health outcomes of the 2006 California heat wave (Knowlton et al., 2009) found that “population acclimatization and adaptive capacity influenced risk” (p. 61) and confirmed that older people and young children were the most likely to suffer health problems. This analysis suggests that community and individual adaptation (for example, air conditioning and use of community cooling centers) can be an effective mitigation strategy during severe heat waves.

Individual physiological factors also interact with exposure to heat. Underlying chronic medical conditions (for example, cardiovascular disease, obesity) exacerbate susceptibility (McGeehin and Mirabelli, 2001; Diaz et al., 2002b), as do medications that affect the body’s thermoregulatory capacity (Bouchama, 2004). Thus, effective interventions to reduce the health impacts of heat should also include targeting those who have multiple risks because of pre-existing health conditions.

Social isolation and limited income are also associated with heat-related illness among older people. Klinenberg’s (2002) Heat Wave documented the toll of the 1995 Chicago heat wave on socially isolated, physically impaired older Chicagoans. In reference to the 2003 European heat wave, Bouchama (2004) described the lethal combination of social isolation with psychiatric, pulmonary, and cardiovascular conditions among older victims. Knowlton and colleagues (2009) argued that the combination of low socioeconomic status and social isolation led to a failure of “adaptive capacity” (p. 61) in some areas of central California during the 2006 Southwestern heat wave.

In sum, research on heat waves suggests that interventions to mitigate the impact of changing climate should target older people with multiple risk factors (health conditions, small social networks, lower socioeconomic status). On the other hand, Kovats and Ebi (2006) point out that the European experience demonstrates that older people with more risk factors for heat-related illness are less likely to use community centers and less able to take protective action on their own because their adaptive capacity is reduced. Klinenberg (2002) found that many older Chicago adults did not take advantage of community cooling centers because of fear of crime.

Hurricanes

Climate change is likely to be associated with the occurrence of more frequent and severe hurricanes. Studies of Hurricane Andrew, the six Florida hurricanes in 2004– 2005, and Hurricane Katrina have contributed new information about how exposure to climate change may disproportionately affect older people. This research suggests that the effects will be more severe among older people who have reduced or declining adaptive capacity, including those who are disabled, poor, chronically ill, or socially isolated.

What is more, an analysis of county-level census and spatial-hazards data in the U.S. shows that older people are more likely to be exposed to natural hazards (Zimmerman et al., 2007). About 20 percent of older people reside in a county where a hurricane or large tropical storm is likely to make landfall over a ten-year period. These data also suggest that there is a higher concentration of low-income older people in these at-risk counties (a situation that may worsen in the future as those with means relocate to safer areas farther away). Also, because of the concentration of older people in these counties, there are also a number of long-term- care facilities, a special cause for concern when evacuation is ordered (Hyer et al., 2006).

Older people are also disproportionately more likely to die as a result of hurricanes. For example, as a result of Hurricane Andrew, older people were more likely to die of indirect causes, such as heart attacks during evacuation (Combs et al., 1996). When flooding occurs, as during Hurricane Katrina, those who have physical impairments and who lack social contacts or personal transportation are much more likely to be victims (Sherman and Shapiro, 2005; Fernandez et al., 2002). Seventy-four percent of the deaths related to Hurricane Katrina were among those age 60 and older, and 50 percent of these were among people over age 75, figures that resulted in efforts to develop specific approaches to evacuating frail and vulnerable older people (Hyer et al., 2006).

A complicating factor is that relatively healthy community-dwelling older people may be less responsive to hurricane warnings, may have physical impairments that make preparation more difficult, and may be less connected to community assistance resources (Donner and Rodriguez, 2008). Despite a sophisticated warning system in Florida, during the 2004 hurricane season when six hurricanes made landfall in the state, older people were no more likely than younger people to heed evacuation warnings (Smith and McCarty, 2009). The latter finding, based on a sample survey of the most affected areas in Florida, implies that older people do not consider themselves to be at special risk, or perhaps that they perceive the burden of evacuation to be too great, especially considering the worry of leaving property unattended and the difficulty of seeking shelter away from home.

Air pollution

Studies of the health effects of ambient air pollution, especially tropospheric ozone and fine particulates, have primarily focused on physiological susceptibilities to pollution that occur more frequently among older people, particularly those with chronic illness. Bateson and Schwartz (2004) found heightened risk of death in the Chicago area from high levels of particulate matter among people with any type of heart or lung disease, and also among older people with a history of myocardial infarction or diabetes. Similar patterns of susceptibility have also been reported for older people exposed to black smoke (Filleul et al., 2004). The influence of social factors has also been examined. Martins and colleagues (2004) found that socioeconomic deprivation increased the rate of mortality related to particulate matter in Sào Paulo, Brazil. However, Bateson and Schwartz (2004) did not replicate the finding in the Chicago area. Filleul and colleagues (2004) reported that deaths attributable to black smoke were more likely among those who lived alone.

Where Do We Go from Here?

The evidence that climate change will potentially adversely affect older people disproportionally is compelling. If the rapidly increasing older population worldwide is to be protected from the effects of climate change to the greatest degree possible, greater knowledge is our most important weapon. The type of knowledge needed is that which can be more effectively translated into health forecasting, urban planning and growth management, residential modifications, effective communication with diverse audiences, and disaster response. In order to develop effective translation strategies, it is important that researchers intensify their investigations of the mechanism of effects on older people’s health to better understand physiological susceptibility factors associated with the diseases of aging and frailty, and their explorations of the social factors associated with more or less capacity to adapt to changing environmental conditions. This research will then need to be translated into strategies to educate older people about risks and strategies like home modification or relocation to avoid or mitigate the risks.

One set of critically important research questions has to do with risk and vulnerability. What are trends in migration patterns of older Americans to coastal and other ecologically sensitive areas? Vulnerable subgroups of the older population are more physiologically susceptible to environmental health problems. How can we best identify specific differences in risk? Greater attention to the effects of climate change on socially and economically vulnerable populations should be made a priority.

In addition, better knowledge about how to assist older people and minimize their susceptibility to the hazards resulting from climate change is urgently needed. Older people require better information regarding environmental threats to health (both those directly related to climate change and others). What communication strategies work best with different groups of older people? Research is needed on evacuation planning for frail community-dwelling older people (and other vulnerable populations). What best practices exist related to evacuation planning? Are registries of vulnerable older people useful? How can technology (e.g., geographic information systems, electronic medical records) be of use in evacuations of frail or otherwise vulnerable older people? Further, there is anecdotal evidence that some older people resist social services in general and, more specifically, assistance in dealing with potential disasters. What do we know about resistance to disaster planning and evacuation, and how might such barriers be overcome?

The basic sense of the term vulnerability is susceptibility to damage or harm (Liverman, 1994), as when the capacity of individuals and social groups to respond and adapt to an external stressor is challenged (Kelly and Adger, 2000). Climate change and its effects increase vulnerability in this sense. However, the impact may be greater on certain high-risk groups. Specifically, climate change will almost certainly exact the heaviest toll among those most socioeconomically disadvantaged, the poor, the very young, and the old (IPCC, 2007b; Paavola and Adger, 2006), who are in turn more vulnerable because of a lack of personal financial resources and institutional impoverishment (Richards, 2003). The effects of climate change on the sources of health for older populations—notably access to food, water, housing, and social support—exhibit similar differential impacts on various populations.

The projected climatechange- related exposures are likely to affect the health of millions of people, particularly those with low adaptive capacity, including many older people. As noted above, increases in malnutrition, death due to extreme weather events, and frequency of cardiovascular disease from increased ozone, as well as altered distribution of disease vectors, will increase the need for adaptive strategies at individual, community, and societal levels. Adverse effects resulting from a changing climate will raise questions of justice as scarce resources are allocated. Many analysts consider placing the needs of the most vulnerable first as a strategy for the fairest adaptation (Paavola and Adger, 2006), with interventions targeted for those with less capacity to adapt. It would be prudent, however, for the United States and other nations to collectively mitigate further emissions of greenhouse gases into the atmosphere, stabilize concentrations at safe levels, and institute adaptive strategies to protect the global population. All of these efforts would serve to minimize early effects on especially vulnerable people, including older adults.

David Filiberto, Ph.D., is research associate, Cornell Institute for Translational Research on Aging; Elaine Wethington, Ph.D., is associate professor, Department of Human Development; Karl Pillemer, Ph.D., is Hazel E. Reed Professor, Department of Human Development, and director, Cornell Institute for Translational Research on Aging; Nancy M. Wells, Ph.D., is associate professor, Design and Environmental Analysis; Mark Wysocki is senior lecturer, Department of Earth and Atmospheric Sciences; and Jennifer True Parise is a research assistant, all at Cornell University, Ithaca, N.Y.

References

Bateson, T. F., and Schwartz, J. 2004. “Who Is Sensitive to the Effects of Particulate Air Pollution on Mortality? A Case-Crossover Analysis of Effect Modifiers.” Epidemiology 15(2): 143–9.

Intergovernmental Panel on Climate Change (IPCC). 2007a. “Summary for Policymakers.” In S. Solomon et al., eds., Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK, and New York: Cambridge University Press.